Regulating system for high capacity boilers



NOV. 8, 1932. w, DE BAUFRE 1,887,147

REGULATING SYSTEM FOR HIGH CAPACITY BOILERS Filed Jan. 28, 1929 3Sheets-Sheet 1 V INVENTOR Wr' Y ATTORNEYS REGULATING SYSTEM FOR HIGHCAPACITY BOILERS Filed Jan. 28, 1929 5 Sheets-Sheet 2 lllllll y lyiqTORBY I 6 7 Nov. 8, 1932. w. DE BAUFRE 1,837,147

REGULATING SYSTEM FOR HIGH CAPACITY BOILERS Filed Jan. 28; 1929 aSheets-Sheet a INVENTOR ATTORNEYS WILLIAM L. DE BAUFBE, OF ORANGE, NEW

Patented Nov. 8, 1932 UNITED STATES PATENT OFFICE JERSEY, ASSIGNOR TOINTERNATIONAL COMBUSTION ENGINEERING CORPORATION, OF NEW YORK, N. Y., ACORPORATION OF DELAWARE REGULATING SYSTEM' FOR HIGH CAPACITY BOILERSApplication filed January 28, 1929. Serial No. 335,448.

This invention relates to the regulation of feed water supply to boilersto ensure adequate supply of water in the boiler under all operatingconditions and is especially useful in high capacity installationsoperated at high rating, such, for example, as installations where thereis a large amount of evaporating surface subject to radiant heat.

The nature, objects, and advantages of my invention will be following.

In boilers operating at very high ratings, such as those of the steamgenerator type, there is a tendency for undesirable fluctuations tooccur in steam pressure and steam generation due to the fact that theweight of water contained in the boiler is small relative to the rate atwhich it is evaporated. Large fluctuations of water level in the steamdrum occur which have been diflicult to control, even with automaticfeed Water regulators.

In known automatic feed water regulators in which a single regulator isemployed connected to the steam drum of the boiler in the manner of theusual boiler gage glass, there are wide and violent fluctuations in therate of feed which accentuate the pressure fluctuations caused by suddenchanges in the demand for steam. This is so because in such devices therate of feed is almost, if not completely, shut off by the rise in thewater level in the steam drum with a sudden increase in the demand forsteam. Then as the water level begins to drop, the opening of the feedvalve by the regulator causes an inflow of cold water which absorbs heatand there by causes a further drop in level and a further increase infeed. As a consequence, the regulator control over-runs the normalposition corresponding to the steam demand.

When the water level starts to rise by reason of the excess feed, thecutting down of the cold feed accentuates the rise. It will be seen,therefore, that this action causes fluctuations in the feed whichproduce troublesome variations in the steam pressure and water level inboilers working atv high ratings.

One of the objects of my invention is to overcome such difliculties andto ensure ade understood from the quate and proper supply of feed waterto the boiler.

How the foregoing together with such other objects and advantages as mayhereinafter appear or are incident to my invention are realized isillustrated in preferred form in the accompanying drawings wherein Fig.1 is a more or less diagrammatic seetional elevation thru a boilerillustrating the application of a feed Water regulating systemconstructed in accordance with one form of vmy invention and If thebottom connection to the gage glass k be made to a lower point in theboiler, how ever, the gage glass will show a lower water level thancorresponds to the level within the steam drum. This is due to the factthat the level within any gage glass is the surface of solid water inone leg of a U- tube, while the boiler drums, tubes, etc., form theother leg containing a mixture of steam and water. In other words thesaid one leg contains a headof solid water equivalent to the head ofmixture of steam and water in the other leg. To balance the column ofsteam and water within the boiler requires a shorter column of solidwater within the gage glass and connections. The difference is affectedby the inertial and frictional resistance to circulation within theboiler and by the difference between the temperature within the boilerand in the gage glass connections. In any given case,.the difl'erencebetween the levels indicated by the ordinary gage glass and the gageglass connected much below the water level, is roughly proportion- 21 tothe rate of steam generation at any given steam pressure. A reduction insteam pressure increases the difierence in levels due to the greatervolume of the steam bubbles produced, thus decreasing the density of themixture within the boiler and increasing the resistance to circulationtherein. If the new gage glass be connected to the lowermost drum orheader, its water level above that point will be a measure of the totalWeight of water contained in the boiler irrespective of the rate ofsteam generation and steam pressure except as affected by circulationresistance.

Referring now to Fig. 1 of the drawings, I have illustrated a simpleform of boiler comprising a mud drum A, a steam and water drum B and aplurality of tubes C connecting the drums. Feed water is supplied to thesteam and water drum B by means of the feed pipe D.

An ordinary gage glass 5 is provided for the drum B with which isassociated a regulator 6 of the expansion type comprising in general ametallic expansion tube 7 which operates a valve 8 thru the medium ofthe lever 9 pivoted on the fixed rod 10 and connected at one end to thetube 7 and at its other end to the valve connecting link 11. The amountof steam and water in the tube 7 governs its expansion and contractionand as it expands or contracts the valve is opened or closed as the casemay be.

A second gage glass 12 is connected between the steam space of the drumB and the lower part of the mud drum A and a regulator 13 similar to theregulator 6 is associated therewith which regulator operates a valve 14.

It is to be observed that the weight of th mixture of steam and water inthe drum B governs the level of water in the gauge glass 5 and regulator6 just as much as the weight of the mixture of steam and water in theentire boiler governsthe level of water in gauge glass 12 and regulator13. In neither case does the gauge glass give an absolutely correctindication of the actual level of the water in the boiler. The error,however, is generally proportional to the height of the particularcolumn of mixed steam and water to which the gauge is connected. Theheight of this column in drum B is so small that for all practicalpurposes in this art the indication of the gauge glass 5 is accept: edas correct, and it is known in the art as a level indicator.

For. the same reason the response of regulator 6 to changes inwaterlevel in the steam drum B is considered sufiiciently accurate togive a practical control of feed water supply thereby. 4

In' other words, a gauge glass or regulator of the type shown in Fig. 1,if connected on one side to the steam space of the boiler and on theother side to a point slightly below the normal water level of theboiler, will re spond to changes in weight of water above the lowestpoint of connection. Considered as an accurate index of the level of thewater in the steam drum neither would be absolutely correct,hut thepercentage of error 1 necessary.

is so small that for all practical purposes the gauge glass andregulator are accepted as reflecting the level of water in the steamdrum.

The distance E between the levels in the gage glasses 5 and 12 is ameasure of the rate of steam generation while the distance F is roughlyproportional to the weight of water contained in the boiler. Of course,with no steam generation, the level in 12 will be the same as the levelin 5.

The valves 8 and 14 are located in the feed line and as here shown thevalve 8 is in one branch of the feed line and the valve 14 in another.

It will be clear from the foregoing that the valve 8 is operated by theregulator 6 and the valve 14 from the regulator 13. The latter valvewith its regulator is adjusted to feed water at a somewhat lower ratethan that of steam generation and the deficiency is made up by regulator6 and its valve to maintain the desired level within the steam drum B.

Under steady steam generation, then, regulator 13will admit throughvalve14 from 50 to 90 per cent, say 7 5 per cent. of the feed water required,and regulator 6 will admit through valve 8 the additional 25 per cent.

Should the demand for steam gradually increase, the water level in steamdrum B will fall and the total amount of Water within the boiler becomesless. The levels in both 5 and 12 will fall, resulting in an increase infeed by both regulators.

Should the steam pressure slowly decrease with the same rate of steamgeneration, there will be a tendency for the level to rise in gage glass5 due to the less dense mixture in the boiler caused by the lower steamdensity. Regulator 6 will thereupon slightly close valve 8, reducing thefeed rate. The amount of water contained in the boiler will become less,causing a drop in the level of gage glass 12 and the regulator 13 willslightly open valve 14. The system will settle down with a somewhatincreased portion of the feed water passing through valve 14 and asomewhat lesser portion through valve 8 with the level in the steam drumslightly lower.

Supposing there should be a sudden increase in the demand for steam.This would almost immediately result in a drop in steam supply through8. The level within the steam drum would soon feel the effect of thedecreased supply relative to the steam demand, and as it loweredregulator 6 would gradually open until at a level in the steam drum verynear its previous height the in creased demand would be met by theincreased flow through valves 8 and 14:.

The regulator 13 is not directly afl'ected by a sudden increase in therate of steam generation, but only indirectly and to a secondary extentby the drop in pressure accompanying the increased demand. It acts toincrease slowly the rate of feed with a sudden increase in steam demand,rather than suddenly shutting off the feed as explained hereinbefore inconnection with the operation of known single regulators. It thereforeprovides a steadying action in proportion to the percentage of the feedcontrolled by it.

A throttle valve 146 may be employed to control the limit of feed.

In Fig. 2 I have illustrated a. system similar to that just describedwith a difference appearing in the type of regulator and valve employed,the former being indicated by reference characters 6a and 13a and thelatter by 8a and 14a.

In Fig. 3 I have shown a form of my invention in which the feed valve23a is controlled by the action of two spaced diaphragms 29 and 30located in the casing 31 and dividing it into two end chambers 32 and 33and an intermediate chamber 34. The end chamber 32 communicates with thewater space of the steam and water drum I3 thru means of a connection35, the end chamber 33 communicates with the mud drum A thru means ofthe connection 36 and the intermed ate chamber 34 communicates with thesteam space of the drum B thru means of the connection 37. Theconnection 37 is provided, with a vessel 38 at its highest point, whichvessel is provided with cooling fins to insure condensation of any steamentering from the steam drum. Thus the pressure in the intermediatechamber 34 will always be substantially constant and equal to the headof water from the center of the diaphragm to the bottom of the portion42 of the connection 37 which drains the vessel 38 back to the drum B.

It will thus be seen that the movement of the diaphragm 30 is roughlyproportional to the total weight of water in the boiler and the movementof the diaphragm 29 varies with variations in the weight of water in thesteam drum B". For reasons above pointed out, variations of weight ofwater through the steam drum B above the point of connection of line arefor practical purposes a sufficiently accurate index of the level ofwater in the st am drum B, and movement of diaphragm 29 may thereforealso be said to vary with variations of level of water in the steam drumB. The two diaphragms 29 and 30 are connected through toggle lever means39 to the valve 23a and are separately adj ustable by means of springs40 and 41, respectively. A small leakage around the feed valve 23a keepsthe vessel 38 filled with water to the overflow portion 42 of theconnection 37, the overflow returning to the drum B.

From the foregoing, it will be seen that I have provided a method andapparatus for automatically controlling the rate of feed water supply toa boiler in proportion to the total weight of water contained therein,as well as in accordance with the variation of level in the steam drumwhich enables more steady operation of boiler installations whenproducing very high rates of steam generation.

I claim 1. The method of controlling the water level in a boiler byregulating the water sup ply thereto which comprises supplying part ofthe feed water in accordance with the weight of water in the boilerirrespective of the water level therein, thru the medium of feed watersupply control means responsive to the head of solid water, equivalentto the mixture in the boiler, and part in accordance with control meansresponsive to the level of the water in the boiler.

2. In a system for controlling the water level and water supply in aboiler, means responsive to the level of water in the boiler forcontrolling feed water supply thereto, and means controlling feed watersupply thereto responsive to the level of a column of water which inturn is responsive to the total weight of mixed steam and water insubstantially the entire boiler.

3. In a system for controlling the water level and water supply in aboiler, a feed water supply line, and means controlling the rate of feedthru said line including a valve, means responsive tothe level of waterin the boiler for actuating said valve, a second valve, and meansresponsive to the total head of steam and water mixture in the boilerfor actuating said second valve.

4. In a system for controlling the water level and'water supply in aboiler, a pair of valves for controlling the feed, means responsive tothe level of water-in the boiler for operating one of the valves andmeans responsive to the total head of steam and water mixture in theboiler for operating the other valve.

5. In a system for controlling water supply in a boiler, a pair ofvalves for controlling the feed, means responsive to the level of waterin the boiler for operating one of the valves and means responsive tothe total head of mixed steam and water in the boiler for operating theother Valve, the normal setting of said valves being such that theintermediate chamber, a connection estab hshmg communication between thelower part of the boiler and one end chamber, a connection establishingcommunication between the boiler at a point slightly below the normalwater level thereof and the other end chamber, a connection establishingcommunication between the steam space of the boiler and the intermediatechamber, a vessel in said last mentioned connection for condensing steamentering the connection from the steam space so as to maintain a head ofsolid water in said connection, and means connecting said diaphragms tosaid valve means.

7. In a system for controlling water supply in a boiler, valve means forcontrolling the rate of feed into the boiler, and means for operatingsaid valve means including a casing, a pair of spaced diaphragmsdividing said easing into two end chambers and an intermediate chamber,a connection establishing communication between the lower part of theboiler and one end chamber, a connection establishing communicationbetween the boiler at a point slightly below the normal water levelthereof and the other end chamber, a connection establishingcommunication between the steam space of the boiler and the intermediatechamber, a vessel in said last mentioned connection for condensing steamentering the connection from the steam space so as to maintain a head ofsolid water in said connection, and toggle means connecting saiddiaphragms to said valve means.

8. In a system for controlling water supply in a boiler, valve means forcontrolling the rate of feed into the boiler, and means for operatingsaid valve means including a casing, a pair of spaced diaphragmsdividing said easing into two end chambers and an intermediate chamber,a connection establishing communication between the lower part of theboiler and one end chamber, a connection establishing communicationbetween the boiler at a point slightly below the normal water levelthereof and the other end chamber, a connection establishingcommunication between the steam space of the boiler and the intermediatechamber, a vessel in said last mentioned connection for condensing steamentering the connection from the steam space so as to maintain a head ofsoli d water in said connection, and means connecting said diaphragms tosaid valve means,

together with means for adjusting the aforesaid valve means.

9. In a system for controlling Water supply in a boiler, valve means forcontrolling the rate of feed into the boiler, and, means for operatingsaid valve means including a casing, a pair of spaced diaphragmsdividing said casing into two end chambers and an intermediate chamber,a connection establishing communication between the lower part of theboiler and one end chamber, a connection establishing communicationbetween the boiler at a point slightly below the normal water levelthereof and the other end chamber, a connection establishingcommunication between the steam space of the boiler and the intermediatechamber, a vessel in said last mentioned connection for condensing steamentering the connection from the steam space so as to maintain a head ofsolid water in said connection, and means connecting said diaphragms tosaid valve means, together'witli means for adjusting the aforesaid valvemeans, and means associated with said diaphragms oiiering resistance tomovement thereof.

10. In a system for controlling water supply in a boiler, valve meansfor controlling the rate of feed into the boiler, and means foroperating said valve means including a casing, a pair of spaceddiaphragms dividing said easing into two end chambers and anintermediate chamber, a connection establishing communication betweenthe lower part of the boiler and one end chamber, a connectionestablishing communication between the boiler at a pointslightly belowthe normal water level thereof and the other end chamber, a connectionestablishing communication between the steam space of the boiler and theintermediate chamber, a vessel in said last mentioned connection forcondensing steam entering the connection from the steam space so as tomaintain a head of solid water in said connection, and means connectingsaid diaphragms to said valve means, together with means for adjustingthe aforesaid valve means, and adjustable means associated with saiddiaphragms ofi'ering resistance to movement thereof.

11. The method of controlling the water level in a boiler by controllinga supply of feed water substantially in accordance with the water leveland concurrently controlling a supply of feed water in accordance withthe weight of the mixture of steam and water in the boiler.

12. The method of controlling the water level in a boiler by controllinga portion of the supply of feed water in accordance with s the weight ofthe mixture of steam and water in the boiler and controlling asubstantially smaller portion substantially in accordance with the waterlevel in the boiler.

13. The method of controlling the water level in a boiler by regulatingthe water'supply thereto, which comprises controlling a supply of waterin accordance with the weight of water in substantially the entireboiler and concurrently controlling a supply of. water substantially inaccordance with the weight of water in the steam drum.

14. The method of controlling the water level in a boilerby regulatingthe water supply thereto, which comprises controlling a supply of waterin accordance with the weight of water in substantially the entireboiler, and concurrently controlling a supply of water substantially inaccordance with the weight of water above a point in the boiler slightlybelow the normal water level thereof.

15. The method of controlling the water level in a boiler by regulatingthe water supply thereto, which comprises controlling a supply of waterin accordance with the weight of water above a point substantially atthe lowest part of the boiler and concurrently controlling a supply ofwater substantially in accordance with the weight of water above a pointin the boiler slightly below the normal water level thereof.

' In testimony whereof, I have hereunto signed my name.

WILLIAM L. DE BAUFRE,

